The African elephant, the largest land animal remaining on earth , is of great importance

The African elephant, the largest land animal remaining on earth , is of great importance to African ecosystem(生态系统). Unlike other animals, the African elephant is to a great extent the builder of its environment. As a big plant-eater, it largely shapes the forest-and-savanna(大草原) surroundings in which it lives, therefore setting the terms of existence for millions of other animals that live in its habitat.
It is the elephant's great desire for food that makes it a disturber of the environment and an important builder of its habitat. In its continuous search for the 300 pounds of plants it must have every day, it kills small trees and underbushes, and pulls branches off big trees. This results in numerous open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas. In these open spaces are numerous plants in various stages of growth that attract a variety of other plant-eaters.
Take the rain forests for example. In their natural state, the spreading branches overhead shut out sunlight and prevent the growth of plants on the forest floor. By pulling down trees and eating plants, elephants make open spaces, allowing new plants to grow on the forest floor. In such situations, the forests become suitable for large hoofed plant-eaters to move around and for small plant-eaters to get their food as well.
What worries scientists now is that the African elephant has become an endangered species. If the elephant disappears, scientists say, many other animals will also disappear from vast areas of forest and savanna, greatly changing and worsening the whole ecosystem.
11. What is the passage mainly about?
A. Disappearance of African elephants.
B. Forests and savannas as habitats for African elephants.
C. The effect of African elephants' search for food.
D. The eating habit of African elephants.
12. What does the underlined phrase “setting the terms” most probably mean?
A. Fixing the time. B. Worsening the state.
C. Improving the quality. D. Deciding the conditions.
13. What do we know about the open spaces in the passage?
A. They result from the destruction of rain forests.
B. They provide food mainly for African elephants.
C. They are home to many endangered animals
D. They are attractive to plant-eating animals of different kinds.
14. According to the passage, which of the following statements is TRUE?
A. The African elephant is the largest animal on earth.
B. African elephants have 300 pounds of plants every day, including small trees and underbushes.
C. The African elephant is in a way the builder of the environment like other land animals
D. If the African elephant disappears, the whole ecosystem won’t be affected..
15. The passage is developed mainly by .
A. showing the effect and then explaining the causes
B. pointing out similarities and differences
C. describing the changes in space order
D. giving examples 11-14 CDDB

(答案→)11-14 CDDB 解析：本文主要讲述了非洲大象的食物链对周围环境的影响。11. C 主旨大意题。往往文章的第一段和最后一段都是透漏文章主旨的地方。而本文正是这样。我们从这两段可以读出，这篇文章是关于非洲象寻找食物所带来的影响的，所以应该选择C。12. D 词义猜测题。根据上半句和下文existence for millions of other animals可知。13. D 细节理解题。Open space出现在文中的第二段的第三句和第四句。从第四句中我们可以得知这样的空地很容易吸引各种各样的食草动物，所以选择D。14. B 细节理解题。根据文章第二段的第二句话可判断B为正确答案。

就是这个解释